2,316 research outputs found

    Q2Q_2-free families in the Boolean lattice

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    For a family F\mathcal{F} of subsets of [n]=\{1, 2, ..., n} ordered by inclusion, and a partially ordered set P, we say that F\mathcal{F} is P-free if it does not contain a subposet isomorphic to P. Let ex(n,P)ex(n, P) be the largest size of a P-free family of subsets of [n]. Let Q2Q_2 be the poset with distinct elements a, b, c, d, a<b, c<d; i.e., the 2-dimensional Boolean lattice. We show that 2No(N)ex(n,Q2)2.283261N+o(N),2N -o(N) \leq ex(n, Q_2)\leq 2.283261N +o(N), where N=(nn/2)N = \binom{n}{\lfloor n/2 \rfloor}. We also prove that the largest Q2Q_2-free family of subsets of [n] having at most three different sizes has at most 2.20711N members.Comment: 18 pages, 2 figure

    Neurosurgical implications of the Jugular Vein Nutcracker

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    In the last ten years, a new variant of Eagle Syndrome is emerging and being described: Styloid Jugular Nutcracker (SJN). In SJN, an elongated or vertically directed styloid process causes jugular vein stenosis by compressing the vein against the arch of C1. The clinical consequences appear to be various and misunderstood, ascribable mainly to venous flow impairment and consequent intracranial hypertension. The aim of this paper is to create an overview of Jugular Vein Nutcracker and to focus on its neurosurgical implications. A PRISMA-based literature search was performed to select the most relevant papers on the topic and to realize a mini-review. Future searches in the neurosurgical field should focus on collecting data about further causes of jugular stenosis compression and the association of SJN with cerebrovascular diseases. It would also be interesting to investigate the potential role of primary and secondary prevention, which is unknown so far

    MicroRNA-221 silencing attenuates the degenerated phenotype of intervertebral disc cells.

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    The aim of this study was to investigate the role of an antichondrogenic factor, MIR221 (miR‐221), in intervertebral disc degeneration (IDD), and provide basic information for the development of a therapeutic strategy for the disc repair based on specific nucleic acid based drugs, such as miR‐221 silencing. We established a relatively quick protocol to minimize artifacts from extended in vitro culture, without selecting the different types of cells from intervertebral disc (IVD) or completely disrupting extracellular matrix (ECM), but by using the whole cell population with a part of resident ECM. During the de‐differentiation process miR‐221 expression significantly increased. We demonstrated the effectiveness of miR‐221 silencing in driving the cells towards chondrogenic lineage. AntagomiR‐221 treated cells showed in fact a significant increase of expression of typical chondrogenic markers including COL2A1, ACAN and SOX9, whose loss is associated with IDD. Moreover, antagomiR‐221 treatment restored FOXO3 expression and increased TRPS1 expression levels attenuating the severity grade of degeneration, and demonstrating in a context of tissue degeneration and inflammation not investigated before, that FOXO3 is target of miR‐221. Data of present study are promising in the definition of new molecules useful as potential intradiscal injectable biological agents

    Superselectors: Efficient Constructions and Applications

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    We introduce a new combinatorial structure: the superselector. We show that superselectors subsume several important combinatorial structures used in the past few years to solve problems in group testing, compressed sensing, multi-channel conflict resolution and data security. We prove close upper and lower bounds on the size of superselectors and we provide efficient algorithms for their constructions. Albeit our bounds are very general, when they are instantiated on the combinatorial structures that are particular cases of superselectors (e.g., (p,k,n)-selectors, (d,\ell)-list-disjunct matrices, MUT_k(r)-families, FUT(k, a)-families, etc.) they match the best known bounds in terms of size of the structures (the relevant parameter in the applications). For appropriate values of parameters, our results also provide the first efficient deterministic algorithms for the construction of such structures

    Thalamo-cortical spiking model of incremental learning combining perception, context and NREM-sleep

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    The brain exhibits capabilities of fast incremental learning from few noisy examples, as well as the ability to associate similar memories in autonomously-created categories and to combine contextual hints with sensory perceptions. Together with sleep, these mechanisms are thought to be key components of many high-level cognitive functions. Yet, little is known about the underlying processes and the specific roles of different brain states. In this work, we exploited the combination of context and perception in a thalamo-cortical model based on a soft winner-take-all circuit of excitatory and inhibitory spiking neurons. After calibrating this model to express awake and deep-sleep states with features comparable with biological measures, we demonstrate the model capability of fast incremental learning from few examples, its resilience when proposed with noisy perceptions and contextual signals, and an improvement in visual classification after sleep due to induced synaptic homeostasis and association of similar memories

    Chitin and Its Derivatives: Nanostructured Materials from Different Marine and Terrestrial Sources

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    Chitin is a very abundant polysaccharide that can be obtained from well-known marine sources (crustaceans), but also from terrestrial sources (mushrooms and insects). In the case where animal sources are considered, the material can be obtained by much abundant food or feeding waste. The extraction methodologies were not developed with similar technical readiness levels considering the different sources and the further conversion to chitin nanofibrils and chitosan is also under study, enabling the production of products differentiated for their macromolecular structures and morphology.Chitin nanofibrils from sea food sources were used in sanitary, cosmetic and packaging applications, where their anti-microbial properties and good biocompatibility were very useful. Chitin from mushrooms and sea food was used as starting material in possible coatings for cellulosic and bioplastic substrates. Currently chitin from insects (Hermetia Illucens) is also under study as well as the methodologies for extracting derivatives from it. Infrared analysis is an interesting technique to compare chitins, chitin nanofibrils and chitosan from different sources as well as electron microscopy for studying their morphology. The derivatives of chitin, such as chitosan and chitin nanofibrils, show anti-microbial properties. Hence, their use in several applications, ranging from packaging to sanitary and cosmetics, can conjugate high performance novel products with a reduced environmental concern. The comparison between chitin derivatives from different sources is very useful to address the biopolymers to specific applications, including the agricultural sector. While more and more applications for chitin derivatives will be developed, differences between them should be clarified and correlated to the sources, the methodologies of their production and their physical-chemical properties

    Insulin-like growth factor-1 as predictive factor of difficult laryngoscopy in patients with GH-producing pituitary adenoma: A pilot study

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    Background: Growth hormone (GH)-producing pituitary tumors account for 10 to 15% of pituitary tumors. The hypersecretion of GH may induce changes in the airway anatomy through the activation of Insulin-like Growth factor 1(IGF-1) pathway. We sought investigate the role IGF-1 as a potential predictive factor of difficult laryngoscopy in patients with GH-producing pituitary adenoma. Methods: This study was a single center retrospective study. We included 33 patients undergoing transsphenoidal resection of GH-producing pituitary. We recorded demographic data, el-Ganzouri risk index (EGRI) and modified Look-Evaluate-Mallampati-Obstruction-Neck mobility (mLEMON) score, and pituitary hormone plasma levels. We performed ordinal logistic regression to analyze the relationship between IGF-1 and EGRI, mLEMON, and Cormack-Lehane Grade score and a multiple logistic regression to test the capability of EGRI, mLEMON and IGF-1 levels to predict Cormack-Lehane score. Receiver operating curve (ROC), area under the curve (AUC), and cut-off value of IGF-1 were calculated. Results: Only 14 (42.8%) and 12 (36.36%) patients showed predictive factors of difficult intubation according to EGRI and mLEMON score, respectively. IGF-1 significantly correlated with Cormack-Lehane (p = 0.005879) but not with mLEMON and EGRI (p = 0.3080 and 0.4146, respectively). In multiple regression model IGF-1 correlated only with Cormack-Lehane grade (p = 0.0089). Area under ROC was 0.8571 and cut-off value of IGF-1 was 186.15 ng/ml. Conclusion: Higher IGF-1 levels correlate with the probability of having a higher Cormack-Lehane score; classical bedside scores, such as mLEMON and EGRI, were not able to predict difficult laryngoscopy in our population

    Dark matter searches using superheated liquids

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    Direct detection of dark matter is one of the most important topics in modern physics. It is estimated that 22% of universe matter is composed by dark matter in front of 0.4% of ordinary matter like stars, galaxies planets and all kind of known astrophysical objects. Several kinds of experiments are nowadays involved in detection of one of the more accepted particle candidates to be dark matter: WIMPs (Weakly Interacting Massive Particles). These detectors, using several kinds of techniques: Cryogenic semiconductors, scintillation materials like I Na or noble gas chambers among others, are reporting very interesting but inconclusive results. In this paper a review of detectors that are using the superheated liquid technique in bubble chambers in order to detect WIMPs is reported. Basically, we will report about Coupp (Chicagoland observatory for underground particle physics), PICO that is composed by Coupp and Picasso researchers having the aim to build a ton experiment and also about a new detector named MOSCAB (Materia oscura a bolle) that recently published a first results of a test chamber that uses also superheated liquid technique but as a Geyser chamber.Bou Cabo, M.; Ardid Ramírez, M.; Felis-Enguix, I. (2016). Dark matter searches using superheated liquids. EPJ Web of Conferences. 121(06007):1-8. doi:10.1051/epjconf/201612106007S1812106007Rayleigh L., On the pressure developed in a liquid during the collapse of a spherical cavity (Philos. Mag34, 94, 1917)Plesset M.S., The growth of vapor bubbles in superheated liquid (J. Appl. Phys.25, 9493, 1954)Forster H.K., Growth of vapor bubbles in superheated liquid (J. Appl. Phys.05, 474, 1954)Seitz F. (Phys. Fluids1, 2, 1958)Behnke E. et al., Coupp Collaboration, First dark matter search results from a 4-kg CF3I bubble chamber operated in a deep underground site (Phys. Rev. D86, 2012)Behnke et al., Coupp Collaboration, Direct measurement of the bubble-nucleation energy threshold in a CF3I bubble chamber (Phys. Rev. D88, 2013)Archambault S., Picasso Collaboration, Dark Matter Spin-Dependent Limits for WIMPs Interactions on19F by PICASSO(Phys. Lett. B, 2009)Bertoni R. et al., A new technique for direct investigation of dark matter (Nuclear Instruments and Methods in Physics Research, A, 61–68, 2014)Bou-Cabo M. et al., LOW Radioactivity Techniques 2013 (LRT 2013): Proceedings of the IV International Workshop in Low Radioactivity Techniques, V:1549, 142 – 147Ardid M. et al., MOSCAB: Direct dark matter search using the Geyser technique, Proc. ICHEP 2014 Conf., Nucl. Phys. B: Proc. Supp. (in press

    A comprehensive characterization of Hermetia illucens derived chitosan produced through homogeneous deacetylation

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    The increasing demand for chitin and chitosan is driving research to explore alternative sources to crustaceans. Insects, particularly bioconverters as Hermetia illucens, are promising substitutes as they process food industry waste into valuable molecules, including chitin. Chitosan can be produced by chitin deacetylation: hot deacetylation to obtain a heterogeneous chitosan, the commonly produced, and cold deacetylation to obtain a homogeneous chitosan, not widely available. The two different treatments lead to a different arrangement of the amine and acetyl groups in the chitosan structure, affecting its molecular weight, deacetylation degree, and biological activity. This is the first report on the production and chemical-physical and biological characterization of homogenous chitosan derived from H. illucens larvae, pupal exuviae, and adults. This work, in addition to the report on heterogeneous chitosan by our research group, completes the overview of H. illucens chitosan. The yield values obtained for homogeneous chitosan from pupal exuviae (3 and 7 %) are in the range of insect (2–8 %) and crustaceans (4–15 %) chitosan. The evaluation of the antioxidant activity and antimicrobial properties against Gram-negative (Escherichia coli) and Gram-positive (Micrococcus flavus) bacteria confirmed the great versatility of H. illucens chitosan for biomedical and industrial applications and its suitability as an alternative source to crustaceans
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